The invention relates to an apparatus and a method for operating a sorption system for air-conditioning vehicles, especially electric vehicles. More specifically, the invention relates to a sorption system of the type containing a storage container for a sorbent and a supply container for a sorbate connected with the storage container by a connecting line that can be shut off, in which the sorbent is desorbed in the charging phase by the addition of heat adsorbed from sorbate, and sorbate vapor is adsorbed on the sorbent in the discharge phase, and optionally the heat of adsorption that is released in the sorbent or the heat of evaporation released in the sorbate are used. The invention also relates to a sorption system of the type including a thermally insulated vacuum-tight supply container with sorbate, at least one vacuum-tight storage container containing a sorbent that is thermally insulated, a connecting duct that can be shut off and connects the two containers with one another, and a heater that can be used for desorption and has heat exchange surfaces, one of which is in contact with the sorbate and the other with a sorbent.
A sorption system of these general types are known from DE-OS 41 26 960. The sorption system described therein operates permanently in a vacuum, with the system being evacuated once when manufactured and then being sealed tight for a long time. This requires comprehensive vacuum technology whose elements are expensive and heavy because of the requirements for providing a long-term seal. In the desorption phase, the sorbent is heated electrically. Because of the low thermal conductivity of the sorbent and the small contact area between the heating coil and the porous sorbent, complete desorption of the sorbate from the sorbent and hence the regeneration of the sorption system lasts a very long time. Because of the requirements of the process, the hot gaseous desorbed sorbate is conducted through the steam duct to the supply container containing sorbate cooled in a previous adsorption phase, on whose walls the sorbate then condenses, giving off condensation heat. The amount of heat released is transferred at least partially to the cooled sorbate and heats it, resulting in a loss of heat by cooling when the vehicle interior has a cooling requirement. Moreover, the adsorption rate and hence the air conditioning are mainly controlled by the steam channel being closed to a greater or lesser degree by regulating a shutoff valve located in the steam duct. However, this kind of regulation is relatively costly for controlling the adsorption rate, because mechanical parts must be moved in a vacuum and also wear with frequent use. In addition, a change in the steam channel cross section while the sorbate vapor is passing through constitutes a noise source that adversely affects riding comfort.
An object of the invention is to improve the apparatus and method of the type referred to above in such fashion that rapid cooling or heating can be achieved with vehicle air conditioning and that no manufacturing, weight, or cost disadvantages need to be taken into account; indeed, improvements are made if possible in this regard.
This object is achieved according to the invention by providing an arrangement wherein the sorption unit, composed of a storage container with sorbent, a supply container with sorbate, and a steam duct connecting the containers with one another, is evacuated only to perform an adsorption process employing a vacuum pump and is vented for desorption. The sorbent located in the storage container is traversed by hot air for desorption, said air, moistened with sorbate after passing through, being vented to the environment past the supply container after flowing through a vent line that branches off the steam duct.
By virtue of the invention, as a consequence of hot air flowing through the sorbent that passes completely through the sorbent and comes in direct contact with the sorbate practically everywhere in the sorbent, the- heat transfer to the stored sorbent, and to the sorbate, is considerably increased and hence desorption is accelerated very sharply. Discharging the hot air loaded with sorbate into the open air without pressurizing the sorbate means that the cooled sorbate is not heated and can therefore be cooled even further during the subsequent adsorption process. As a result, more cooling energy is provided by comparison with conventional sorption systems for air conditioning systems, and is accomplished faster and with only a short regeneration phase required for the sorbent.
On the whole, the invention ensures an acceleration of the sorption process, so that heat and cold are available more rapidly for air conditioning. It is not necessary in this regard to keep the sorption unit evacuated during the entire sorption process, so that the individual elements of the sorption unit do not have to be made tight for the long term to hold a vacuum. This permits simple manufacture of the components, and structurally expensive feedthroughs in the vacuum containers can be omitted. Because of the reduced quality requirements regarding vacuum tightness for the components, thinner walls can be used and materials with lower vacuum quality can be used, making the sorption unit lighter and less expensive.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.